1. Preheat the oven to gas mark 4/ 350 degrees F. Grease a loaf pan with butter and line with a parchment paper.
2. In a bowl, sift together plain flour, baking soda and salt.
3. In another bowl, cream together butter and caster sugar.
4. Add in the eggs, buttermilk and banana. Stir well and add in the vanilla essence. Mix all the ingredients thoroughly.
5. Pour the batter into the prepared loaf pan. Bake in the oven for 6nt0 minutes or until golden brown.